This invention relates to a locking device usable in locking systems in buildings, vehicles, furniture, safes, switchgear cabinets, key-operated switches, etc. The invention also relates to a method for preventing the opening of a locking device.
Locking devices with mechanically and electronically controlled blocking or inhibiting elements are known. They have all the properties of conventional, purely mechanical locking devices. The additional, electronically controlled locking system also provides the possibility of individually activating and inhibiting keys. Thus, such mechanical-electronic locking devices lead to additional flexibility in the locking organization.
Electronically controlled locking is based on data transmission between a key-side electronic module and a lock-side electronic module. This data transmission can take place by contact, e.g., by electrical contacts on the key and lock, or without contact, e.g., by electromagnetic induction. Data can be transmitted in only one or in both directions. By means of the transmitted data a check is made in the lock-side electronic module as to whether the inserted key is access authorized. If this is the case, a lock-side motor is activated, which moves an additional, electronically controlled inhibiting element in such a way that it frees or releases the lock cylinder.
Known mechanical-electronic locking devices are particularly susceptible to vibration and/or shock effects, or to magnetic effects. By suitable external actions of these types, it is possible to transfer the electronically controlled inhibiting element from its inhibit position into the free or release position. Thus, the electronically controlled locking means can be opened with purely mechanical and/or magnetic means, without insertion of an appropriate electronically coded key. For this purpose, a constant frequency vibration can be externally applied to the locking mechanism. If the frequency is appropriately chosen, the electronically controlled inhibiting element resonantly vibrates and modifies its position as a result of scarcely foreseeable interactions with other elements. A further unblocking action can be obtained by impacts or blows on the locking mechanism. As is known, a pulse can be formed from monochromatic vibrations, so that the vibration can be looked upon as a special impact case. Vibrations or impulses are propagated as sound waves in the lock cylinder. As a result of the complicated internal structure of the lock cylinder, it is scarcely possible to calculate beforehand its propagation and action on individual elements within the lock cylinder. Further, external influences can take place with magnetic forces. Bypassing of the electronically controlled locking system by external influences is, of course, undesired.
An object of the invention is to provide a mechanical-electronic locking device which is resistant to external influences, particularly vibration and/or shock effects or magnetic actions, and which ensures reliable operation.
The invention is based on an analysis of the mechanical processes taking place when opening an inhibiting or blocking element by vibration and/or shock effects. As a result of these external influences the inhibiting element preferably resonantly vibrates and the necessary restoring forces are exerted by its attachment to the motor. When the locking device is subjected to resonant vibrations, parasitic forces act intermittently on the inhibiting element and on the motor. Mechanisms can come into effect which aid movement of the inhibiting element in one direction and prevent it in the other, in the manner of a ratchet. Such mechanisms can result from asymmetric damping, feedback of other oscillating or vibrating elements, etc. As a result, during its external action, the inhibiting element can be moved in one direction and, in the worst case, toward the xe2x80x9cfree positionxe2x80x9d, i.e., the position in which it releases the lock cylinder. Thus, a sufficiently large number of parasitic impulses of force is enough to transfer the inhibiting element from its inhibit position into the free position.
To prevent the locking device from being opened in this way, according to the invention, at least in the area around the free position, an additional force, termed a xe2x80x9crestoring forcexe2x80x9d, is exerted on the inhibiting element and is opposed to the parasitic forces. If the amount of this restoring force is greater than the critical force, e.g., the maximum parasitic force occurring during a force impulse, the inhibiting element can no longer move in an uncontrolled manner toward the free position.
However, an additional risk is inherent in exerting a restoring force on the inhibiting element. As is known, a mobile mass on which a restoring force acts forms an oscillator with at least one resonant frequency. Such an oscillator can be resonantly vibrated by excitation with a suitable frequency and the amplitude of these vibrations, as a function of the damping present, can be very considerable. Under this effect, the locking device could be undesirably opened by external influences.
In order to prevent this, freely vibrating masses are avoided to the greatest possible extent in the locking device and method according to the invention. For this purpose, the position of the inhibiting element is clearly predetermined by suitable guidance means which prevents resonant vibrations of the mass of the inhibiting element.
The locking device according to the invention has at least one electronically controlled inhibiting element, hereinafter simply referred to as an xe2x80x9cinhibiting elementxe2x80x9d, having at least one degree of freedom of movement. As a result of this inhibiting element, a rotor and stator of the lock cylinder are mutually lockable. If the inhibiting element is to block the locking cylinder, it should be in a specific, first position, hereinafter called the xe2x80x9cinhibit positionxe2x80x9d. In a second position, hereinafter called the xe2x80x9cfree positionxe2x80x9d, the inhibiting element releases or frees the lock cylinder.
The locking device according to the invention has drive means for exerting a working force on the inhibiting element. By means of the working force the inhibiting element can be reversibly transferred from the inhibiting position into the free position and vice versa.
A locking device according to the invention also has guidance means connected to the drive means to clearly determine the inhibiting element position, at least outside the free position.
A locking device according to the invention also has restoring means connected, on the one hand, to a support immovable relative to the stator and, on the other hand, to the inhibiting element. The restoring means exerts a restoring force on the inhibiting element which is directed away from the free position if the inhibiting element is in the area around the free position. According to the invention, the inhibiting element must inhibit or block in the vicinity of the free position.
Beside the inhibit position and the free position, the inhibiting element preferably also has a third defined position, known as the xe2x80x9crest positionxe2x80x9d, in which the restoring means exerts no force on the inhibiting element. The inhibiting element inhibits the lock cylinder in the rest position. The restoring means exerts on the inhibiting element a restoring force directed away from the free position when the inhibiting element is between the free position and the rest position and the inhibiting element inhibits the lock cylinder in the rest position and in positions between the rest position and the free position.
The free position is preferably located in such a way that a maximum working force and/or a maximum distance or travel, i.e., a maximum energy, is required in order to transfer the inhibiting element from the rest position into the free position. It is then substantially impossible to open the locking device solely with vibration and/or shock actions, without operating the drive means. The drive means can exert a working force on the inhibiting element which is higher than the particular restoring force.
The resistance to vibration and/or shock action is additionally increased if the inhibiting position is so positioned that a maximum distance or travel is required in order to transfer the inhibiting element from the inhibit position into the free position. If, e.g., the inhibiting element can perform linear translations along a given path, then preferably the free position is at the first end of the path, the inhibit position is at the second end of the path and the rest position is in the center of the path. The driving-back force always acts toward the center of the path, i.e., toward the rest position, where, according to the invention, the inhibiting element is already exerting an inhibiting action. However, in other embodiments the rest position can coincide with the inhibit position or can be omitted.
In the method of the invention for preventing opening of a locking device by parasitic forces caused by vibration and/or shock effects, to avoid freely vibrating or oscillating masses, the position of the inhibiting element is clearly predetermined by guidance means. At least in the vicinity of the free position, a restoring force is exerted on the inhibiting element which is opposed to the parasitic forces.